The present invention relates to a transcutaneous energy transfer (TET) system and a TET system method of operation.
Transcutaneous energy transfer (TET) systems are used to supply power to devices such as heart pumps implanted internally within a human body. An electromagnetic field generated by a transmitting coil outside the body can transmit power across a cutaneous (skin) barrier to a magnetic receiving coil implanted within the body. The receiving coil can then transfer the received power to the implanted heart pump or other internal device and to one or more batteries implanted within the body to charge the battery.
One of the challenges of such systems is insufficient battery lifetime. The implanted battery may be required to supply the implanted device's entire power demand for one to several hours at a time, such as when the patient does activities that preclude wearing the external TET power unit, such as showering or swimming. When the implanted battery is first implanted into the patient, the battery capacity is large and can meet the power demand for the required amount of time. However, when subjected to frequent charging and discharging, the implanted battery's capacity decreases. With decreased battery capacity, the patient cannot spend as much time without the external TET power unit. Eventually, the battery may need to be replaced so that the patient can go without the external TET power unit for long enough periods of time again.
Until now, premature wear-out of the implanted battery due to frequent charging and discharging of the battery was believed to be unavoidable. Conventional TET systems do not supply power closely in accordance with the time-varying power requirements of implanted devices. As a result, when the implanted device has rapidly fluctuating power demands such as characteristic of circulatory assist pumps including left ventricle assist devices (“LVADs”), the implanted battery is required to supply power for momentary high power demands and the TET system recharges the battery when the momentary power demands ease.